= Runtime Library Notes

== Directory Structure
    sd8516/                  project root
      runtime/
        crt0.sda             startup stub -- CALL main
        librt/               runtime functions
          divhi3.c
          modhi3.c
          divsi3.c
          muldi3.c
          ...
          softfloat/         the SF/DF families
        include/             freestanding headers (mine & what clang supplies)
        tests/               tests with checks


== Prep Work
* Helper scripts were created this time: ''c2sda'', ''c2ll'', ''ll2sda'' and ''runtests''.
* Next I had to modify VC-4 to take .sda files at the command line (to speed the dev cycle).
* Next I created the above directory.
* I will have to modify vc4 to look in ~/.vc4 if the files it needs are not in the pwd.

== Fleshing it out
Many standard implementations reveal deficiencies in instrinfo and iseltargetlowering.

== Test Suite
I collected all the tests into one file.

== Roadmap
* putchar.sda (the only assembly only file so far -- similar to tinyc v1)
* print_str
* print_dec
* lib1 (stuff for missing instructions)
* libctype
* libstr
* libstdlib

then

* stdint.h, limits.h, stddef.h, stdbool.h
* stdalign/stdnoreturn/iso646
* finish string.h (memchr, strncat, strpbrk, strspn, strcspn, strtok)
* safe-string extras (strlcpy/strlcat, strcasecmp/strncasecmp, memmem),
* div/ldiv, rand/srand, qsort/bsearch, assert.h
* official puts/getchar.

Roadmap which requires additional development:

* malloc/free/calloc/realloc
* then strdup/strndup

Phase III
* stdarg.h for varargs and formatted output. very high value target (enables printf)
* printf/sprintf/snprintf/vsnprintf and sscanf.

Later:
* compiler-facing primitives LEA, MOVSX, CMOV, get CASETAB to emit.
* 64-bit integers. __muldi3, __udivdi3/__umoddi3, __divdi3/__moddi3.

Floating Point Roadmap:
* Start writing math.h and see what happens.
* strtod/atof, %f for printf.

File IO Roadmap:
* fopen/fread/fwrite/fseek/fclose and FILE* streams wrapping *(see INT 15h/OPFS/FCB)

Other:
* time.h, calendar math, binding time() to the hardware clock

* Graphics and Sound libraries
* access to PPU and ASU

== Arena Allocator
"A growable, chunked, monotonic region allocator."

This is very similar to the NVAR system I wrote for BASIC. Hanson uses "arena" in C Interfaces and Implementations; the academic literature says "region". "Bump allocator" is the name of the mechanism, advancing a pointer within a chunk, but the whole structure, with chunked growth and free-everything-at-once teardown, is the arena.